fix(timeline): prevent duplicate threads in chronological mixed feeds

[Tlaster]

Chronological mixed timelines could repeat a thread during the initial load: [1…9] was followed by [1…8], even when Bluesky and Mastodon each returned only one remote page. Collapsed parents remained in staging because only the final timeline root rows were counted as consumed.

Include inline-parent IDs in the consumed set before reading staged items again. The SQL query returns only IDs and scopes references to existing roots in the current timeline.

Validation:

• 35 JVM tests passed: ./gradlew :shared:jvmTest --tests '*MixedRemoteMediatorTest' --tests '*PagingTimelineDaoTest'.
• Added two-post and nine-post initial-load regressions; both failed before the fix and pass afterward.
• Added DAO coverage for reference types, timeline isolation, duplicate IDs, and references left behind by deleted roots.
• Ran ktlint format/check on all four changed Kotlin files and git diff --check.

Fixes #2166.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-07T03:00:33.737073Z	6056e80	PR opened

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